The reproductive epidemiology project emphasizes the development and application of methods for measuring human reproductive damage. Reproductive damage includes infertility, subclinical pregnancy loss, clinically-recognized pregnancy loss (or spontaneous abortion), impaired fetal growth, and low birthweight. Each of these outcomes can be caused by environmental factors, and each represents a possible endpoint for detecting effects of toxins on human health. This year we have completed our prospective study of subclinical pregnancy loss among a group of 221 North Carolina women who were attempting pregnancy. These women collected daily urine specimens for up to six months. Using a very sensitive assay for the hormone hCG, we identified 198 pregnancies at about 8 to 10 days after fertilization. 22% of these pregnancies failed to last long enough to be recognized by the woman or her physician. If we also include losses that occurred to recognized pregnancies, then 31% of all assay detected pregnancies failed to survive to term. We are analyzing these data further for evidence of any effects of common exposures (such as caffeine or alcohol) on the risk of having a pregnancy loss. We are planning a new study of early pregnancy loss among women occupationally exposed to a reproductive toxin such as lead, in order to test how useful this endpoint might be in environmental studies. The pregnancy study also offers data on factors that influence a woman's capacity to conceive. For example, we have found a strong relation between caffeine consumption and lower fertility. Work has progressed in other areas as well. In collaboration with Norwegian scientists we have made progress in developing methods for the analysis of birthweight and infant mortality, using the Norwegian Medical Births Registry.